Automatic gain control for lidar for autonomous vehicles

ABSTRACT

A LIDAR system includes an emitter array configured to illuminate a field of view, a detector array configured to image the field of view, and a control circuit. The emitter array includes one or more emitter elements that are configured to emit respective optical signals responsive to respective emitter control signals. The detector array includes one or more detector elements configured to output respective detection signals responsive to light incident thereon. The control circuit is configured to generate the respective emitter control signals based on the respective detection signals and respective spatial correlations of the one or more emitter elements and the one or more detector elements with respect to the field of view. Related devices and methods of operation are also discussed.

CLAIM OF PRIORITY

This application claims priority from U.S. Provisional Application No.62/654,972, filed with the United States Patent and Trademark Office onApr. 9, 2018, the disclosure of which is incorporated by referenceherein.

FIELD

The subject matter herein relates generally to three-dimensional (3D)imaging, and more specifically to LIDAR (Light Detection And Ranging)systems for 3D imaging.

BACKGROUND

Time of flight (ToF) based imaging is used in a number of applicationsincluding range finding, depth profiling, and 3D imaging (e.g., LightDetection And Ranging (LIDAR), also referred to herein as lidar). FlashLIDAR, which can use a pulsed light emitting array to emit light forshort durations over a relatively large area to acquire images based onsensing of the reflected light emission, may allow for solid-stateimaging of a large field of view. In specific applications, the sensingof the reflected light may be performed using a detector array ofsingle-photon detectors, such as a Single Photon Avalanche Diode (SPAD)detector array. SPAD detector arrays may be used as solid-statedetectors in imaging applications where high sensitivity and timingresolution are desired.

However, to illuminate a large field of view (which may include longrange and/or low-reflectivity targets and in bright ambient lightconditions) and receive a recognizable return or reflected opticalsignal therefrom (also referred to herein as an echo signal), higheroptical emission power may be required, which may be inefficient and/orundesirable. That is, higher emission power (and thus higher powerconsumption) may be required in some applications due to the relativelyhigh background noise levels from ambient and/or other non-LIDAR emitterlight sources (also referred to therein as a noise floor). This can beproblematic in some applications, e.g., unmanned aerial vehicle (UAV),automotive, and industrial robotics. For example, higher emission powermay result in increased power consumption, while higher optical energymay fail to meet eye-safety requirements. Also, heat generated from thehigher emission power may alter the optical performance of the lightemitting array and/or may negatively affect reliability.

SUMMARY

Some embodiments described herein provide methods, systems, and devicesincluding electronic circuits to address the above and other problemswithout substantially impacting overall system performance of a LIDARsystem including one or more laser emitter elements (includingsemiconductor lasers, such as surface- or edge-emitting laser diodes;generally referred to herein as emitters) and one or more light detectorelements (including semiconductor photodetectors, such as photodiodes;generally referred to herein as detectors).

According to some embodiments, a LIDAR system includes a control circuitthat is configured to receive respective detection signals that areoutput from operation of detector elements and control generation ofrespective control signals for operation of emitter elements (and/or thedetector elements) based on the respective detection signals. Thecontrol signals are configured to control temporal and/or spatialoperation of individual emitter elements of an emitter array and/orindividual detector elements of a detector array, based on the detectionsignals from one or more detector elements of the detector array andpredetermined spatial correlations of or correspondences between theindividual emitter and detector elements (and/or sub-arrays thereof)with respect to the field of view.

According to some embodiments, a LIDAR system includes an emitter arrayconfigured to illuminate a field of view, a detector array configured toimage the field of view, a driver circuit, and a control circuit. Theemitter array includes one or more emitter elements that are configuredto emit respective optical signals responsive to respective emittercontrol signals. For example, the emitter array may include two or moreemitter sub-arrays, each including respective subsets of the emitterelements. The driver circuit may include respective driver sub-circuitscoupled to the respective emitter sub-arrays. The detector arrayincludes one or more detector elements that are configured to outputrespective detection signals responsive to light incident thereon. Thecontrol circuit is configured to generate the respective emitter controlsignals (via the respective driver sub-circuits or otherwise) based onthe respective detection signals and respective spatial correlations ofthe one or more emitter elements and the one or more detector elementswith respect to the field of view.

In some embodiments, the respective optical signals differ at differentspatial locations of the emitter array based on the respective detectionsignals and the respective spatial correlations of the one or moreemitter elements with respect to the field of view.

In some embodiments, the respective detection signals output from firstand second subsets of the detector elements indicate first and secondreflectances of first and second targets in the field of view,respectively. The first reflectance may be less than or greater than thesecond reflectance.

In some embodiments, the respective emitter control signals areconfigured to activate first and second subsets of the emitter elementsat different spatial locations of the emitter array to emit first andsecond optical signals, respectively, based on the respective spatialcorrelations thereof with the first and second subsets of the detectorelements, respectively. The first and second subsets of the emitterelements may be first and second sub-arrays of the respective emittersub-arrays. In some embodiments, the first and second optical signalshave first and second power levels, respectively, where the first powerlevel is greater than the second power level.

In some embodiments, the control circuit is configured to generaterespective detector control signals based on the respective detectionsignals and the respective spatial correlations of the one or moreemitter elements and the one or more detector elements with respect tothe field of view.

In some embodiments, the respective detector control signals areconfigured to activate the first and second subsets of the detectorelements for first and second durations of time or sensitivity levels,respectively, where the first duration or sensitivity level is greaterthan the second duration or sensitivity level.

In some embodiments, the respective detection signals output from firstand second subsets of the detector elements indicate the first andsecond reflectances, respectively, responsive to the first target beinglocated at a greater distance from the detector array than the secondtarget.

In some embodiments, the respective detection signals output from firstand second subsets of the detector elements indicate the first andsecond reflectances, respectively, responsive to the first target beingof lower or higher reflectivity than the second target.

In some embodiments, the respective detection signals output from firstand second subsets of the detector elements indicate a combination ofdistance from the detector and reflectivity such that the photon fluxfrom the first detector is lower or higher than the photon flux from thesecond target.

In some embodiments, the respective detection signals indicate relativemotion between the LIDAR system and a target in the field of view. Thecontrol circuit is configured to estimate an expected position of thetarget in the field of view based on the relative motion. The respectiveoptical signals differ based on the expected position of the target andthe respective spatial correlations of the emitter elements with respectto the field of view.

In some embodiments, the LIDAR system is configured to be coupled to anautonomous or other vehicle such that the emitter and detector arraysare oriented relative to an intended direction of travel of the vehicle.

According to some embodiments, a method of operating a LIDAR systemincludes performing operations by a control circuit. The operationsinclude receiving, from a detector array that is configured to image afield of view, respective detection signals that are output from one ormore detector elements of the detector array responsive to lightincident thereon; generating, by a driver circuit including respectivedriver sub-circuits, respective emitter control signals based on therespective detection signals and respective spatial correlations of oneor more emitter elements of an emitter array and the one or moredetector elements with respect to the field of view; and transmitting,to the emitter array, the respective emitter control signals to activatethe one or more emitter elements to emit respective optical signals toilluminate the field of view. For example, the emitter array may includerespective emitter sub-arrays, each including one or more emitterelements, and the respective driver sub-circuits may provide therespective emitter control signals to the respective emitter sub-arrays.

According to some embodiments, a LIDAR system includes a control circuitthat is configured to provide respective emitter control signals to oneor more emitter elements to emit respective optical signals atrespective power levels. The respective emitter control signals areoutput based on receiving respective detection signals from one or moredetector elements indicating respective reflectances of one or moretargets in a field of view thereof, and based on respective spatialcorrelations of the one or more emitter elements and the one or moredetector elements with respect to the field of view.

In some embodiments, the LIDAR system further includes an emitter arrayincluding first and second emitter sub-arrays including first and secondsubsets of the emitter elements, respectively, and a driver circuitincluding first and second driver sub-circuits coupled to the first andsecond emitter sub-arrays, respectively. The control circuit isconfigured to operate the first and second driver sub-circuits togenerate the respective emitter control signals to control operation offirst and second subsets of the emitter elements at first and secondspatial locations of the emitter array to emit first and second opticalsignals having different first and second power levels, respectively,based on the respective detection signals and the respective spatialcorrelations.

In some embodiments, the one or more targets include first and secondtargets and the respective reflectances indicate first and secondreflectances thereof, respectively. The first reflectance may be lessthan the second reflectance, and the first power level may be greaterthan the second power level.

In some embodiments, the LIDAR system further includes a detector arrayincluding the detector elements. The control circuit is furtherconfigured to output respective detector control signals that areconfigured to control operation of first and second subsets of thedetector elements at first and second spatial locations of the detectorarray for first and second durations of time or sensitivity levels,respectively, based on the respective detection signals and therespective spatial correlations.

In some embodiments, the LIDAR system includes an algorithm or circuitthat is configured to track relative motion of targets based ondetection signals corresponding to one or more frames and control theillumination power at respective spatial locations of the emitter arraybased on the expected position of the targets in one or more subsequentframes.

In some embodiments the control circuit implements an algorithm orcircuitry whereby, even if a highly reflective target is imaged ordetected at a zone of illumination in the field of view, the controlcircuit is configured to generate a periodic pulse or sequence of pulsesto operate the emitter elements having a spatial location thatcorresponds to the zone to emit higher power light in order to check ordetect whether less reflective targets may be present in that zone. Thatis, responsive to the first reflectance being greater than the secondreflectance, the control circuit may generate the respective emittercontrol signals such that the first power level is greater than thesecond power level for detection of less reflective targets in aparticular zone having a more reflective target.

In some embodiments the control circuit implements an algorithm orcircuitry that is configured to generate the respective emitter controlsignals to provide two levels of illumination for each illumination zonein the field of view.

In some implementations the control circuit implements an algorithm orcircuitry that is configured to generate the respective emitter controlsignals to provide more than two levels of illumination for eachillumination zone in the field of view. For example, a subset of theemitter elements that are spatially correlated to a respectiveillumination zone may be configured to emit optical signals having oneof a plurality of discrete illumination levels (for example, threedifferent illumination levels) based on the respective detection signalsfrom a subset of the detectors that are spatially correlated to therespective illumination zone.

Other devices, apparatus, and/or methods according to some embodimentswill become apparent to one with skill in the art upon review of thefollowing drawings and detailed description. It is intended that allsuch additional embodiments, in addition to any and all combinations ofthe above embodiments, be included within this description, be withinthe scope of the invention, and be protected by the accompanying claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram illustrating example components of a time offlight LIDAR measurement system or circuit in accordance with someembodiments described herein.

FIG. 2 is a block diagram illustrating an example control circuit thatreceives detection signals output from respective detector elements andgenerates control signals to respective emitter elements in response inaccordance with some embodiments described herein.

FIG. 3 is a block diagram illustrating an example emitter arrayincluding respective optical emitter elements in accordance withembodiments described herein.

FIG. 4 is a block diagram illustrating an example detector arrayincluding respective detector elements in accordance with embodimentsdescribed herein.

FIG. 5. is a block diagram illustrating an example of an automotiveapplication of a time of flight LIDAR measurement system or circuitconfigured to provide zonal illumination control in accordance with someembodiments described herein.

FIG. 6 is a flowchart illustrating example operations performed by acontrol circuit in a time of flight LIDAR measurement system or circuitin accordance with some embodiments described herein.

FIG. 7 is a block diagram illustrating a further example of a time offlight LIDAR measurement system or circuit configured to provide zonalillumination control in accordance with some embodiments describedherein.

FIGS. 8 and 9 are block diagrams illustrating example systemconfigurations including sub-arrays of emitters and associatedsub-driver circuits in accordance with some embodiments describedherein.

DETAILED DESCRIPTION OF EMBODIMENTS

A LIDAR system may include an array of emitter elements and an array ofdetector elements, or a system having a single emitter element and anarray of detector elements, or a system having an array of emitters anda single detector element. A flash LIDAR system may acquire images byemitting light from an array of emitter elements for short durations(pulses) over a field of view (FoV) and detecting the reflected lightemission. A non-flash or scanning LIDAR system may generate image framesby raster scanning light emission (continuously) over a field of view,for example, using a point scan or line scan to emit the necessary powerper point and sequentially scan to reconstruct the full field of view(FOV) from detection of the reflected light emission.

Some embodiments described herein arise from recognition that someconventional LIDAR systems may operate at higher or maximum power levelsto image longer-range and/or lower-reflectivity targets to account forworst-case conditions, but such worst-case conditions may not occur ormay occur for only a small part of the field of view in a majority ofimaging scenarios.

Embodiments described herein are thus directed to adaptive illuminationschemes that can reduce emitter power in LIDAR operation, for flash ornon-flash/scanning LIDAR applications. In particular, embodiments of thepresent disclosure provide emitters and associated control circuits thatare configured to adaptively adjust output power of one or more emitterelements of the emitter array, for example, respective sub-arrays of theemitter array, based on the detection signals from one or more detectorelements of the detector array and a known spatial correlation of orcorrespondence between the individual emitter and detector elements (orsub-arrays thereof) with respect to the field of view.

An example of a flash LIDAR system or circuit 100 is shown in FIG. 1.The system 100 includes a control circuit 105, a timing circuit 106, anemitter array 115 including a plurality of emitters 115 e, and adetector array 110 including a plurality of detectors 110 d (forexample, an array of single-photon detectors). The emitter elements 115e of the emitter array 115 respectively emit a radiation pulse (forexample, through a diffuser or optical filter 114) at a time controlledby a timing generator or driver circuit 116. In particular embodiments,the emitters 115 e may be pulsed light sources, such as LEDs or lasers(such as vertical cavity surface emitting lasers (VCSELs)). The maximumoptical power output of the light source 115 e may be selected togenerate a signal-to-noise ratio of the echo signal from the farthest,least reflective target at the brightest background illuminationconditions that can be detected in accordance with embodiments describedherein.

In some embodiments, each of the emitter elements 115 e in the emitterarray 115 is connected to and controlled by a respective driver circuit116. In other embodiments, respective groups of emitter elements 115 ein the emitter array 115 (e.g., emitter elements 115 e in spatialproximity to each other), may be connected to a same driver circuit 116.The driver circuit or circuitry 116 may include one or more drivertransistors, which are configured to control the timing and amplitude ofthe optical emission signals that are output from the emitters 115 e. Adiffuser 114 is illustrated to increase a field of view of the emitterarray 115 by way of example.

Light emission output from one or more of the emitters 115 e impinges onand is reflected by one or more targets 150, and the reflected light isdetected as an optical signal (also referred to herein as an echo signalor echo) by one or more of the detectors 110 d (e.g., via one or morelenses 112), converted into an electrical signal representation, andprocessed (e.g., based on time of flight) to define a 3-D point cloudrepresentation 170 of the field of view 190.

More particularly, the detector array 110 generates respective detectionsignals indicating the respective times of arrival of photons in thereflected optical signal, and outputs the respective detection signalsto the control circuit 105. In some embodiments, the control circuit 105may include a pixel processor that measures the time of flight of theillumination pulse over the journey from the emitter array 115 to atarget 150 and back to the detector array 110 (i.e., the time betweenemission of the optical signal by the emitter array 115 and the time ofarrival of the reflected optical signal or echo at the detector array110, as indicated by the respective detection signals) and calculatesthe distance to the target 150. Operations of LIDAR systems inaccordance with embodiments of the present invention as described hereinmay be performed by one or more processors or controllers, such as thecontrol circuit 105 of FIG. 1. Portions or an entirety of the controlcircuits described herein may be integrated in the emitter array 115and/or detector array 110 in some embodiments.

Still referring to FIG. 1, each of the detector elements 110 d of thedetector array 110 is connected to a timing circuit 106. The timingcircuit 106 may be phase-locked to the driver circuitry 116 of theemitter array 115. The sensitivity of each of the detector elements 110d or of groups of detector elements 110 d (described herein withreference to respective sensitivity levels) may be controlled by thetiming circuit 106. For example, when the detector elements 110 dinclude reverse-biased photodiodes, avalanche photodiodes (APD), PINdiodes, and/or Geiger-mode Avalanche Diodes (SPADs), the reverse biasmay be adjusted by the timing circuit 106, whereby, the higher theoverbias, the higher the sensitivity level. When the detector elements110 d include integrating devices such as a CCD, CMOS photogate, and/orphoton mixing device (pmd), the charge integration time may be adjustedby the timing circuit 106 such that a longer integration time translatesto higher sensitivity.

In some embodiments, the light emission from individual emitters 115 eis not mixed with that of other emitters 115 e. In some embodiments, thelight emission from individual emitters is mixed, e.g., by using thediffuser 114, but some spatial correlation is maintained between theemission profile of individual emitter elements 115 e and the diffusedlight illuminating the scene. Without loss of generality, embodimentsdescribed below assume that the diffuser shown in FIG. 1 is not present.

In some embodiments, multiple or all of the emitters 115 e are activatedsimultaneously. Reflected signals from various targets 150 return to thedetector array 110 and are detected by one or more of the detectors 110d, which output respective detection signals in response.

Although illustrated with reference to a flash LIDAR system, it will beunderstood that embodiments described herein may include non-flash orscanning (also referred to as “line scanning” or “point scanning”without loss of generality to other types of scanning) LIDAR systems aswell. In a scanning LIDAR system or circuit, a target may be detected byone or more detectors 110 d of the detector array 110 that are spatiallyarranged to image a respective angular position of the field of view(FOV) 190, and the control circuit 105 and/or driver circuit 116 maycontrol the scanning of the emitter(s) 115 e to alter the power of theoptical signals emitted therefrom levels (e.g., to reduce power level)each time the emitter(s) 115 e scan the angular position. That is,emitter power may be differently controlled at different angular orrotational positions of a FOV based on detection signals received fromdetectors having respective spatial correlations to the angularpositions.

Embodiments described herein are directed to operations for controllingthe temporal and/or spatial operation of the individual emitter elements115 e and/or the individual detector elements 110 d based on detectionsignals from one or more of the individual detector elements 110 d ofthe detector array and known or predetermined spatial correlations ofthe individual emitter 115 e and detector elements 110 d with respect tothe field of view.

In some embodiments, both flash and scanning LIDAR systems as describedherein may employ motion estimation algorithms or circuits to detect andestimate the position of moving targets (relative to the LIDAR system)over the field of view, and adjust output signals from the emittersbased on expected positions of the object and spatial correlations withcorresponding areas of the field of view. For example, the controlcircuit 105 may receive detection signals from respective detectorelements 110 d of the detector array 110 that indicate relative motionof a target 150 over the field of view 190, e.g., based on differencesin the indicated reflectances and/or ranges in sequentially receiveddetection signals (e.g., corresponding to sequential image frames) fromrespective detectors 110 d at respective spatial locations of thedetector array 110. The control circuit 105 may determine that thetarget 150 is moving and may estimate an expected position of the target150 in the field of view 190 based on the sequentially-receiveddetection signals, and the control circuit 105 (via the driver circuit116) may generate respective emitter control signals to adjust the powerlevels of the optical signals output from one or more of the emitters115 e that are spatially correlated to the expected position(s) of thetarget 150 (e.g., in a next or future image frame) in the field of view190. The control circuit 105 may likewise output respective emittercontrol signals that adjust the power levels of optical signals outputfrom one or more of the emitters 115 e that are spatially correlated tothe position(s) of the field of view 190 at which the target 150 wasdetected (as indicated by the detection signals fromspatially-correlated detectors 110 d), but is expected to leave, basedon the detected relative motion and expected position. That is, thespatial operation of the emitter elements 115 e described herein may bebased on actual or expected positions of a target 150, and thus, thespatial correlation between the field of view 190 and the detector 110 dfrom which a particular detection signal is output may not necessarilycorrespond to the spatial correlation between the field of view 190 andthe emitter 115 e from which an optical signal is emitted based on orresponsive to that particular detection signal.

In some embodiments, the control circuit 105 (or other processor andmemory associated therewith) may store predetermined spatialcorrelations between specific regions of the field of view that areilluminated by specific emitters in the array, and specific regions ofthe field of view that are imaged by specific detectors in the detectorarray. For example, a calibration process may be performed to determineemitter-detector correlation, e.g., by activating individual or groupsof emitters and storing results of detection by individual or groups ofdetectors (e.g., as indicated by the point cloud) in a lookup table inthe memory. Reflected light may be distinguished for emitter/detectorcorrelation purposes using a variety of techniques for operatingrespective emitters and/or detectors, including but not limited todifferent pulse encoding, different phase encoding, different emissionwavelengths, different optical diffusion, and different opticalfiltering.

In some embodiments, respective detection signal outputs from one ormore detectors of the array are input to a control circuit, such as amicrocontroller or microprocessor, which feeds back a respective controlsignal to the driver circuitry of the respective emitter having thespatial correlation to that detector. An example of a control circuit205 that receives detection signals 211 output from respective detectorelements 110 d of the detector array 110 as feedback and generatescontrol signals 215 to respective emitter elements (and/or controlsignals 210 to respective detector elements) in response is shown inFIG. 2. The control circuit 205 of FIG. 2 may represent one or morecontrol circuits, for example, the control circuit 105 described above,an emitter control circuit (which may include the driver circuitry 116)that is configured to provide emitter control signals 215 to the emitterarray 115, and/or a detector control circuit (which may include thetiming circuitry 106) that is configured to provide the detector controlsignals 210 to the detector array 110 as described herein. In someembodiments, the control circuit 205 may include a sequencer circuitthat is configured to coordinate operation of the emitters 115 e anddetectors 110 d. More generally, the control circuit 205 may include oneor more circuits that are configured to generate respective emittercontrol signals 215 that control the respective power levels of theoptical signals output from the emitters 115 e, and/or to generaterespective detector control signals 210 (such as strobe signals) thatcontrol the timing and/or durations of activation of the detectors 110 d(e.g., for respective strobe windows between the pulses of the opticalsignals from the emitters 115 e), based on the detection signals 211from one or more of the detectors 110 d and known or predeterminedspatial correlations or correspondence between subsets of the emitters115 e and subsets of the detectors 110 d with respect to the field ofview.

In some embodiments, the respective detection signals 211 output fromthe detector array 110, which may be used as feedback signals to controltemporal and/or spatial operation of the emitters 115 e and/or detectors110 d as described herein, may indicate one of the following scenarios:(i) an optical signal is detected within a desired signal-to-noise level(SNR)(where the signal may correspond to the emission wavelength(s) ofthe optical signals output from the emitters and noise may be attributedto effects of ambient light) and below detector saturation; (ii) anoptical signal is detected below a desired SNR and below detectorsaturation; (iii) an optical signal is detected above a desired SNR andbelow detector saturation; (iv) the detector is saturated; (v) no targetis detected.

The respective detection signals 211 output from the detector array 110are input to the control circuit 205. In response to receiving thesefeedback signals 211 from one or more detector elements 110 d indicatingthe scenarios (i) to (v) above, the control circuit 205 may beconfigured to generate and provide emitter control signals 215 (e.g.,via the driver circuit 116) to control operation of one or more of theemitters 115 e based on the spatial correlations to respective detectors110 d from which the respective detection signals 211 were received asfollows, for the scenarios (i) to (v) above, respectively: (i) maintainemission energy for the optical signals output from the emitter(s) 115e; (ii) increase emission energy for the optical signals output from theemitter(s) 115 e; (iii) decrease emission energy for the optical signalsoutput from the emitter(s) 115 e; (iv) decrease emission energy for theoptical signals output from the emitter(s) 115 e; (v) drive a presetenergy for the optical signals output from the emitter(s) 115 e, wherethe preset energy is less than the maximum energy.

In some embodiments, in response to receiving the feedback signals 211from one or more detector elements 110 d indicating the scenarios (i) to(v) above, the control circuit 205 may be configured to generaterespective detector control signals 210 to control operation of one ormore (spatially-correlated) detectors 110 d to change its gain. Gaincontrol can vary based the type of detector 110 d, for example byaltering a reverse bias and/or a charge integration time of the detector110 d. In some embodiments, the detector control signals 210 may alterthe gain of a respective spatially-correlated detector 110 d (alone orin combination with generation of the emitter control signals 215) asfollows, for the scenarios (i)-(v) above, respectively: (i) maintaingain/sensitivity level of the respective detector(s) 110 d; (ii)increase gain/sensitivity level of the respective detector(s) 110 d;(iii) decrease gain/sensitivity level of the respective detector(s) 110d; (iv) decrease gain/sensitivity level of the respective detector(s)110 d; (v) modify operation of the respective detector(s) 110 d toprovide nominal gain/sensitivity level.

FIG. 3 and FIG. 4 illustrate an example emitter array 315 includingrespective optical emitter elements 315 e and an example detector array410 including respective detector elements 410 d in accordance withembodiments described herein, respectively. The example emitter array315 and detector array 410 shown in FIGS. 3 and 4 may represent theemitter array 115 and detector array 110 of FIG. 1, respectively. FIGS.3 and 4 illustrate a one-to-one correlation or correspondence of emitterelements 315 e and detector elements 410 d by way of example only, andit will be understood that fewer or more emitter elements 315 e ordetector elements 410 d (and thus, one-to-many or many-to oneemitter-detector correlations) may be provided in accordance withembodiments described herein.

In some embodiments, the control circuit 205 is configured todifferently operate respective emitter elements 315 e and/or detectorelements 410 d at different spatial positions of the emitter array 310and/or detector array 410 (also referred to herein as controllingspatial operation of the elements of the arrays). In particularembodiments, the control circuit 205 is configured to differentlyoperate respective emitter elements 315 e at different spatial positionsof the emitter array 310 to emit light/optical signals with differentpower levels, based on respective detection signals received or fed-backfrom corresponding detector elements 410 d of the detector array 410.

For example, in an operating environment including a more distant ordimmer target having a lower reflectance and a more proximate orbrighter target having a higher reflectance (relative to the LIDARsystem 100), the control circuit 205 may be configured to selectivelyoperate a subset 301 of the emitter elements 315 e (whose light emissionis directed towards the proximate target) to emit optical signals havinga lower power level responsive to receiving detection signal(s) from oneor more spatially-correlated detector elements 410 d (e.g., of subset401) indicating the higher reflectance, and may selectively activate adifferent subset 302 of the emitter elements 315 e (whose light emissionis directed towards the distant target) to emit light having a higherpower level responsive to receiving detection signal(s) from one or morespatially-correlated detector elements 410 d (e.g., of subset 402)indicating the lower reflectance. This is illustrated in the operationof the example emitter array 310 shown in FIG. 3, where one subset 301of the emitter elements 315 e (on the left side of the illustratedemitter array 310) is operated to emit optical signals at a lower powerlevel (shown by smaller starbursts) than another subset 302 of theemitter elements 315 e (on the right side of the illustrated emitterarray 310), which are operated to emit optical signals at a higher powerlevel (shown by larger starbursts).

That is, based on individual feedback signals from correspondingdetector elements (or from a point cloud representation based thereon),control circuits described herein may be configured to apply differentcurrent levels to individual emitter elements, based on spatial positionin the array and/or a range of a target, which may be used addressdynamic range issues in some embodiments.

In some embodiments, the control circuit 205 is configured to operaterespective emitter elements 315 e and/or detector elements 410 d withdifferent timing or temporal constraints (also referred to herein ascontrolling temporal operation of the elements of the arrays). Forexample, responsive to operating one or more emitter elements 315 e(e.g., of subset 301) to emit a first pulse of photons, the controlcircuit 205 may be configured to control a timing and/or sensitivity ofoperation of the spatially-correlated detector element(s) 410 d (e.g.,of subset 401) for a first period or “window” of time (e.g., xnanoseconds), for example, using a time gating scheme. Likewise,responsive to operating one or more emitter elements 315 e (e.g., ofsubset 302) to emit a second pulse of photons, the control circuit 205may be configured to control a timing and/or sensitivity of operation ofthe spatially-correlated detector element(s) 410 d (e.g., of subset 402)for a second period/window of time (e.g., y nanoseconds) that isdifferent from the first time period/window. This is illustrated in theoperation of the example detector array shown in FIG. 4, where onesubset 401 of the detector elements 410 d (on the left side of theillustrated detector array 410) is operated for a shorter window/lesserduration of time (shown by pulse width t1) or using a lower reverse biassignal to provide reduced sensitivity, while another subset 402 of thedetector elements 410 d (on the right side of the illustrated detectorarray 410) is operated for a longer window/greater duration of time(shown by pulse width t2) or using a higher reverse bias signal toprovide greater sensitivity. The subset 402 of the detector elements 410d may be operated for the longer window/greater duration of time and/orhigher sensitivity level responsive to previously-received detectionsignals from the subset 402 indicating a target having less reflectancein a portion of the field of view to which the subset 402 is spatiallycorrelated, while the subset 401 of the detector elements 410 d may beoperated for the shorter window/lesser duration of time and/or lowersensitivity level responsive to previously-received detection signalsfrom the subset 401 indicating a target having greater reflectance in aportion of the field of view to which the subset 401 is spatiallycorrelated.

In embodiments described herein, a detector time gate or strobe windowmay refer to the respective durations of activation and deactivation ofone or more detectors (e.g., responsive to respective strobe signalsfrom a control circuit) over the temporal period or time between pulsesof the emitter(s) (which may likewise be responsive to respectiveemitter control signals from a control circuit). The time between pulses(which defines a laser cycle, or more generally emitter pulse frequency)may be selected or may otherwise correspond to a desired imagingdistance range for the LIDAR system. Each strobe window may bedifferently delayed relative to the emitter pulses, and thus maycorrespond to a respective portion or subrange of the distance range.Each strobe window may also correspond to a respective image acquisitionsubframe (or more particularly, point cloud acquisition subframe,generally referred to herein as a subframe) of an image frame. That is,each image frame includes a plurality of subframes, each of thesubframes samples or collects data for a respective strobe window overthe temporal period, and each strobe window covers or corresponds to arespective distance subrange of the distance range.

Zonal illumination control provided by some flash LIDAR systems inautomotive applications is shown in FIG. 5. The system 500 of FIG. 5provides a wide FOV 590 over a distance range, for example, a 120×30 FOVcovering a 200 meter (m) distance range (relative to theemitter/detector of the LIDAR system 500, illustrated as mounted in avehicle 560). Such a system 500 may operate by flooding the FOV 590 withactive illumination (e.g., as provided by vertical cavity surfaceemitting laser (VCSEL) pulses output from an array 515 of VCSELs 515 e)and imaging the FOV 590 (e.g., as provided by operation of an array 510of SPADs 510 d), both spatially (covering the full FOV 590) andtemporally (covering the full FOV 590 throughout period of operation).

In the example of FIG. 5, subsets or sub-arrays 501 d, 502 d, 503 d ofthe detectors 510 d of the detector array 510 are arranged to imagerespective portions of the FOV 590. Likewise, subsets 501 e, 502 e, 503e of the emitters 515 e of the emitter array 515 are arranged toilluminate respective portions of the FOV 590, with spatial correlationsor correspondences 501 c, 502 c, 503 c between the subsets or sub-arrays501 e, 502 e, 503 e of the emitters 515 e and the subsets 501 d, 502 d,503 d of the detectors 510 d relative to the FOV 590, respectively. TheFOV 590 is illustrated with reference to gridlines to highlight thespatial correlations with emitters 515 e and detectors 510 d, which areillustrated with reference to similar gridlines. The spatialcorrelations 501 c, 502 c, 503 c may also be described herein withreference to zones 501 e, 502 e, 503 e of the emitters array 515, zones501 d, 502 d, 503 d of the detector array 510, and/or zones of the FOV590.

Example operation of the system 500 of FIG. 5 will be described withreference to the flowchart of FIG. 6. Referring now to FIGS. 5 and 6,the control circuit 505 generates initial emitter control signals 515 cto operate subsets 501 e, 502 e, 503 e of the emitters 515 e to emitoptical signals having a same or similar power level (e.g., a higher ormaximal power level) at block 605. Echo signals corresponding to theoptical signals are detected by subsets 501 d, 502 d, and 503 d of thedetectors 510 d, and respective detection signals 511 from the detectors510 d are received at the control circuit 505 at block 610. Therespective detection signals 511 may indicate the presence of alower-reflectance target 550 b towards a central portion of the FOV 590and a higher-reflectance target 550 a towards one side of the FOV 590,for example, based on return signal strengths indicated by therespective detection signals 511 from the subsets 502 d and 501 d of thedetectors 510 d that are spatially correlated (indicated by 502 c and501 c) to the central and side portions of the FOV 590, respectively.The reflectances of the targets 550 a and 550 b may indicate thereflectivities of respective surfaces of the targets 550 a and 550 band/or the respective distances of the targets 550 a and 550 b from thedetector array 510. That is, the reflectances indicated by the detectionsignals described herein may indicate relative characteristics of thetargets and/or relative distances of the targets with respect to theimaging system.

In response, the control circuit 505 generates respective emittercontrol signals 515 c to operate the subsets 501 e, 502 e, 503 e of theemitters 515 e to emit optical signals having different power levelsbased on the detection signals 511 and the spatial correlations 501 c,502 c, 503 c between the subsets 501 e, 502 e, 503 e of the emitters andthe subsets 501 d, 502 d, 503 d of the detectors 510 d with respect tothe FOV 590 at block 615. In particular, based on the indication of thelower-reflectance target 550 b at the central portion of the FOV 590,the subset 502 e of the emitters 515 e that are spatially correlated tothe central portion of the FOV 590 (indicated by 502 c) are operated toemit optical signals with a higher output power (illustrated by largerstarbursts). Likewise, based on the indication of the higher-reflectancetarget 550 a at the side portion of the FOV 590, the subset 501 e of theemitters 515 e that are spatially correlated to the side or peripheralportion of the FOV 590 (indicated by 501 c) are operated to emit opticalsignals with a lower output power (illustrated by smaller starbursts).Also, based on the indication of the absence of a target at the otherside portion of the FOV 590, the subset 503 e of the emitters 515 e thatare spatially correlated to the other side or peripheral portion of theFOV 590 (indicated by 503 c) are operated to emit optical signals with apredetermined output power that is less than the maximal output power(illustrated by mid-sized starbursts).

In some embodiments, the control circuit 505 may be configured tointermittently or periodically operate all emitters 515 e to emitoptical signals at higher or maximal power in order to detect dimmertargets (which may not have been previously or otherwise detected) atblock 605, and respective detection signals 511 received responsive tothe maximal power emission at block 610 may be used to control thesubsequent emission power of respective subsets of the emitters 515 e atblock 615, based on the relative power levels of the detection signals511. For example, operation of the emitters 515 e for range acquisitionoperations at block 615 may occur more frequently (e.g., 30 times persecond), while maximal power (max-flash) at block 605 may occur lessfrequently (e.g., once per second).

FIG. 7 is a block diagram illustrating another example of a time offlight LIDAR measurement system or circuit configured to provide zonalillumination control in accordance with some embodiments describedherein. As shown in FIG. 7, respective echo signals are detected byfirst and second subsets 710 a and 710 b of detectors 710 d located atrespective positions (illustrated by “x” symbols) of a detector array710, and respective detection signals 711 are output from the detectorarray 710 to a zonal automatic gain control (AGC) control circuit 705.The respective detection signals 711 indicate the presence (and relativereflectances) of first and second targets 750 a and 750 b at regions ofa field of view corresponding to the respective positions of the firstand second subsets 710 a and 710 b, for example, based on return signalstrengths indicated by the respective detection signals outputtherefrom. In response, the control circuit 705 generates respectiveemitter control signals 715 c to operate first and second subsets 715 aand 715 b of emitters 715 e at corresponding spatial positions of anemitter array 715 to emit first and second optical signals havingdifferent power levels (illustrated by differently-sized starburstsymbols) to differently illuminate the regions of the field of view atwhich the targets 750 a and 750 b were detected, based on the respectivedetection signals 711 and the spatial correlations between the subsets715 a, 715 b of the emitters 715 e and the subsets 710 a, 710 b of thedetectors 710 d with respect to the FOV. In some embodiments, thecontrol circuit may be further configured to operate the emitters anddetectors in combination with operations for coverage and detection ofdifferent distance ranges (e.g., 0-50 meters, 50-90 meters), e.g., basedon times corresponding to the ranges, as described for example in U.S.Provisional Patent Application No. 62/799,116 filed Jan. 31, 2019, thedisclosure of which is incorporated by reference herein.

In some embodiments, an array of feedback control circuits and/or drivecircuits as described herein may be integrated on a same chip. Forexample, the chip may be an LCD driver chip with very high parallelism,which may be configured to simultaneously drive the array of emitters toemit optical signals with different output power levels based on thespatial correlations of the emitters and the detectors (from whichrespective detection signals are received) relative to the FOV imagedthereby.

Thus, in some embodiments described herein, maximal emission may belimited to those emitter elements which illuminate the dimmest targets,and overall emission power may be significantly reduced by selectiveoperation of one or more of the emitter elements based on feedback fromspatially-correlated one(s) of the detector elements. In someembodiments, the detection signal-based feedback operations describedherein may be performed for sub-regions or sub-arrays of the emitterarray (including a subset of the emitters) and/or sub-regions orsub-arrays of the detector array (including a subset of the detectors).

FIGS. 8 and 9 illustrate system configurations 800, 900 that providerespective (emitter and/or detector) control signals to sub-arrays ofemitters 815 e, 915 e. The emitters 815 e, 915 e are described in FIGS.8 and 9 with reference to vertical cavity surface emitting lasers(VCSELs) and high voltage (HV) and ground connections by way of example,but it will be understood that emitter arrays as described herein arenot so limited.

As shown in FIGS. 8 and 9, arrays 815, 915 of VCSELs 815 e, 915 e arelaid out such that some VCSELs 815 e, 915 e are connected in series andin close vicinity (e.g., as a string of emitters), providing respectiveemitter sub-arrays 815 s, 915 s. Each string or sub-array 815 s, 915 sis connected to a respective driver sub-circuit 816 s, 916 s, each ofwhich may include a power transistor and local control circuitry thatare configured to provide respective emitter control signals to therespective sub-arrays 815 s, 915 s. The driver sub-circuit 816 s, 916 smay also include one or more capacitors (implemented as capacitor banks975 laid out at a periphery of the array 915 in FIG. 9) for local chargestorage with a reduced or minimal inductive path to the VCSELs 815 e,915 e. Each driver sub-circuit 816 s, 916 s is electrically connected toan external control circuit (e.g., control circuit 105 of FIG. 1). Insome implementations, one or more capacitors are placed on the substratehaving the emitter array 815, 915 thereon (or in close proximity to thesubstrate) such that sufficient charge is collected in the capacitors toprovide for the required temporal drive of the VCSEL pulses as theemitter control signals, without excessive inductance effects.

Lidar systems and arrays described herein may be applied to ADAS(Advanced Driver Assistance Systems), autonomous vehicles, UAVs(unmanned aerial vehicles), industrial automation, robotics, biometrics,modeling, augmented and virtual reality, 3D mapping, and security. Insome embodiments, the emitter elements of the emitter array may bevertical cavity surface emitting lasers (VCSELs). In some embodiments,the emitter array may include a non-native substrate having thousands ofdiscrete emitter elements electrically connected in series and/orparallel thereon, with the driver circuit implemented by drivertransistors integrated on the non-native substrate adjacent respectiverows and/or columns of the emitter array, as described for example inU.S. Patent Application Publication No. 2018/0301872 to Burroughs etal., filed Apr. 12, 2018, with the United States Patent and TrademarkOffice, the disclosure of which is incorporated by reference herein.

Various embodiments have been described herein with reference to theaccompanying drawings in which example embodiments are shown. Theseembodiments may, however, be embodied in different forms and should notbe construed as limited to the embodiments set forth herein. Rather,these embodiments are provided so that this disclosure is thorough andcomplete and fully conveys the inventive concept to those skilled in theart. Various modifications to the example embodiments and the genericprinciples and features described herein will be readily apparent. Inthe drawings, the sizes and relative sizes of layers and regions are notshown to scale, and in some instances may be exaggerated for clarity.

The example embodiments are mainly described in terms of particularmethods and devices provided in particular implementations. However, themethods and devices may operate effectively in other implementations.Phrases such as “example embodiment”, “one embodiment” and “anotherembodiment” may refer to the same or different embodiments as well as tomultiple embodiments. The embodiments will be described with respect tosystems and/or devices having certain components. However, the systemsand/or devices may include fewer or additional components than thoseshown, and variations in the arrangement and type of the components maybe made without departing from the scope of the inventive concepts. Theexample embodiments will also be described in the context of particularmethods having certain steps or operations. However, the methods anddevices may operate effectively for other methods having differentand/or additional steps/operations and steps/operations in differentorders that are not inconsistent with the example embodiments. Thus, thepresent inventive concepts are not intended to be limited to theembodiments shown, but are to be accorded the widest scope consistentwith the principles and features described herein.

It will be understood that when an element is referred to or illustratedas being “on,” “connected,” or “coupled” to another element, it can bedirectly on, connected, or coupled to the other element, or interveningelements may be present. In contrast, when an element is referred to asbeing “directly on,” “directly connected,” or “directly coupled” toanother element, there are no intervening elements present.

It will also be understood that, although the terms first, second, etc.may be used herein to describe various elements, these elements shouldnot be limited by these terms. These terms are only used to distinguishone element from another. For example, a first element could be termed asecond element, and, similarly, a second element could be termed a firstelement, without departing from the scope of the present invention.

Furthermore, relative terms, such as “lower” or “bottom” and “upper” or“top,” may be used herein to describe one element's relationship toanother element as illustrated in the Figures. It will be understoodthat relative terms are intended to encompass different orientations ofthe device in addition to the orientation depicted in the Figures. Forexample, if the device in one of the figures is turned over, elementsdescribed as being on the “lower” side of other elements would then beoriented on “upper” sides of the other elements. The exemplary term“lower”, can therefore, encompasses both an orientation of “lower” and“upper,” depending of the particular orientation of the figure.Similarly, if the device in one of the figures is turned over, elementsdescribed as “below” or “beneath” other elements would then be oriented“above” the other elements. The exemplary terms “below” or “beneath”can, therefore, encompass both an orientation of above and below.

The terminology used in the description of the invention herein is forthe purpose of describing particular embodiments only and is notintended to be limiting of the invention. As used in the description ofthe invention and the appended claims, the singular forms “a”, “an” and“the” are intended to include the plural forms as well, unless thecontext clearly indicates otherwise.

It will also be understood that the term “and/or” as used herein refersto and encompasses any and all possible combinations of one or more ofthe associated listed items. It will be further understood that theterms “include,” “including,” “comprises,” and/or “comprising,” whenused in this specification, specify the presence of stated features,integers, steps, operations, elements, and/or components, but do notpreclude the presence or addition of one or more other features,integers, steps, operations, elements, components, and/or groupsthereof.

Embodiments of the invention are described herein with reference toillustrations that are schematic illustrations of idealized embodiments(and intermediate structures) of the invention. As such, variations fromthe shapes of the illustrations as a result, for example, ofmanufacturing techniques and/or tolerances, are to be expected. Thus,the regions illustrated in the figures are schematic in nature and theirshapes are not intended to illustrate the actual shape of a region of adevice and are not intended to limit the scope of the invention.

Unless otherwise defined, all terms used in disclosing embodiments ofthe invention, including technical and scientific terms, have the samemeaning as commonly understood by one of ordinary skill in the art towhich this invention belongs, and are not necessarily limited to thespecific definitions known at the time of the present invention beingdescribed. Accordingly, these terms can include equivalent terms thatare created after such time. It will be further understood that terms,such as those defined in commonly used dictionaries, should beinterpreted as having a meaning that is consistent with their meaning inthe present specification and in the context of the relevant art andwill not be interpreted in an idealized or overly formal sense unlessexpressly so defined herein. All publications, patent applications,patents, and other references mentioned herein are incorporated byreference in their entireties.

Many different embodiments have been disclosed herein, in connectionwith the above description and the drawings. It will be understood thatit would be unduly repetitious and obfuscating to literally describe andillustrate every combination and subcombination of these embodiments.Accordingly, the present specification, including the drawings, shall beconstrued to constitute a complete written description of allcombinations and subcombinations of the embodiments of the presentinvention described herein, and of the manner and process of making andusing them, and shall support claims to any such combination orsubcombination.

Although the invention has been described herein with reference tovarious embodiments, it will be appreciated that further variations andmodifications may be made within the scope and spirit of the principlesof the invention. Although specific terms are employed, they are used ina generic and descriptive sense only and not for purposes of limitation,the scope of the present invention being set forth in the followingclaims.

1. A LIDAR system, comprising: an emitter array configured to illuminatea field of view, the emitter array comprising emitter elementsconfigured to emit respective optical signals responsive to respectiveemitter control signals, wherein respective subsets of the emitterelements define respective emitter sub-arrays; a driver circuitcomprising respective driver sub-circuits coupled to the respectiveemitter sub-arrays; a detector array configured to image the field ofview, the detector array comprising detector elements configured tooutput respective detection signals responsive to light incidentthereon; and a control circuit configured to operate the respectivedriver sub-circuits to generate the respective emitter control signalsbased on the respective detection signals and respective spatialcorrelations of the emitter elements and the detector elements withrespect to the field of view.
 2. The LIDAR system of claim 1, whereinthe respective optical signals differ based on the respective detectionsignals and the respective spatial correlations of the emitter elementswith respect to the field of view.
 3. The LIDAR system of claim 2,wherein the respective detection signals output from first and secondsubsets of the detector elements indicate first and second reflectancesof first and second targets in the field of view, respectively, whereinthe first reflectance is less than the second reflectance.
 4. The LIDARsystem of claim 3, wherein the respective emitter control signals areconfigured to activate first and second subsets of the emitter elementsat different spatial locations of the emitter array to emit first andsecond optical signals, respectively, based on the respective spatialcorrelations thereof with the first and second subsets of the detectorelements, respectively.
 5. The LIDAR system of claim 4, wherein thefirst and second optical signals have first and second power levels,respectively, wherein the first power level is greater than the secondpower level.
 6. The LIDAR system of claim 3, wherein the control circuitis configured to generate respective detector control signals based onthe respective detection signals and the respective spatial correlationsof the emitter elements and the detector elements with respect to thefield of view.
 7. The LIDAR system of claim 6, wherein the respectivedetector control signals are configured to activate the first and secondsubsets of the detector elements for first and second durations of timeor sensitivity levels, respectively, wherein the first duration orsensitivity level is greater than the second duration or sensitivitylevel.
 8. The LIDAR system of claim 3, wherein the respective detectionsignals output from first and second subsets of the detector elementsindicate the first and second reflectances, respectively, responsive tothe first target being located at a greater distance from the detectorarray than the second target.
 9. The LIDAR system of claim 2, whereinthe respective detection signals indicate relative motion between theLIDAR system and a target in the field of view, wherein the controlcircuit is configured to estimate an expected position of the target inthe field of view based on the relative motion, and wherein therespective optical signals differ based on the expected position of thetarget and the respective spatial correlations of the emitter elementswith respect to the field of view.
 10. The LIDAR system of claim 1,wherein the LIDAR system is configured to be coupled to a vehicle suchthat the emitter and detector arrays are oriented relative to anintended direction of travel of the vehicle.
 11. A method of operating aLIDAR system, the method comprising: performing, by a control circuit,operations comprising: receiving, from a detector array that isconfigured to image a field of view, respective detection signals thatare output from detector elements of the detector array responsive tolight incident thereon; generating, by respective driver sub-circuitscoupled to respective emitter sub-arrays, respective emitter controlsignals based on the respective detection signals and respective spatialcorrelations of emitter elements of an emitter array and the detectorelements with respect to the field of view, wherein respective subsetsof the emitter elements define the respective emitter sub-arrays; andtransmitting, to the emitter array, the respective emitter controlsignals to activate the emitter elements to emit respective opticalsignals to illuminate the field of view.
 12. The method of claim 11,wherein the respective optical signals differ based on the respectivedetection signals and the respective spatial correlations of the emitterelements with respect to the field of view.
 13. The method of claim 12,wherein the respective detection signals output from first and secondsubsets of the detector elements indicate first and second reflectancesof first and second targets in the field of view, respectively, whereinthe first reflectance is less than the second reflectance.
 14. Themethod of claim 13, wherein the respective emitter control signals areconfigured to activate first and second subsets of the emitter elementsat different spatial locations of the emitter array to emit first andsecond optical signals, respectively, based on the respective spatialcorrelations thereof with the first and second subsets of the detectorelements, respectively.
 15. The method of claim 13, wherein therespective optical signals comprise first and second optical signalshaving first and second power levels, respectively, wherein the firstpower level is greater than the second power level.
 16. The method ofclaim 13, wherein the operations further comprise: generating respectivedetector control signals based on the respective detection signals andthe respective spatial correlations of the emitter elements and thedetector elements with respect to the field of view.
 17. The method ofclaim 16, wherein the respective detector control signals are configuredto activate the first and second subsets of the detector elements forfirst and second durations of time or sensitivity levels, respectively,wherein the first duration or sensitivity level is greater than thesecond duration or sensitivity level.
 18. A LIDAR system, comprising: acontrol circuit configured to provide respective emitter control signalsto one or more emitter elements to emit respective optical signals atrespective power levels, based on receiving respective detection signalsfrom one or more detector elements indicating respective reflectances ofone or more targets in a field of view thereof, and based on respectivespatial correlations of the one or more emitter elements and the one ormore detector elements with respect to the field of view.
 19. The LIDARsystem of claim 18, further comprising: an emitter array comprisingfirst and second emitter sub-arrays including first and second subsetsof the emitter elements, respectively; and a driver circuit comprisingfirst and second driver sub-circuits coupled to the first and secondemitter sub-arrays, respectively, wherein the control circuit isconfigured to operate the first and second driver sub-circuits togenerate the respective emitter control signals to control operation ofthe first and second subsets of the emitter elements at first and secondspatial locations of the emitter array to emit first and second opticalsignals having different first and second power levels, respectively,based on the respective detection signals and the respective spatialcorrelations.
 20. The LIDAR system of claim 19, wherein the one or moretargets comprise first and second targets and the respectivereflectances indicate first and second reflectances thereof,respectively, wherein the first reflectance is less than the secondreflectance, and wherein the first power level is greater than thesecond power level.
 21. The LIDAR system of claim 18, furthercomprising: a detector array comprising the detector elements, whereinthe control circuit is further configured to output respective detectorcontrol signals that are configured to control operation of first andsecond subsets of the detector elements at first and second spatiallocations of the detector array for first and second durations of timeor sensitivity levels, respectively, based on the respective detectionsignals and the respective spatial correlations.